1. Field of the Invention
The invention relates to a semiconductor component, and more particularly to a trench gate metal-oxide-semiconductor field effect transistor (MOSFET).
2. Description of Related Art
Trench MOSFET has been widely applied in power switch devices, such as power supplies, rectifiers, low-voltage motor controllers, or so forth. In general, the trench MOSFET is often resorted to a design of vertical structure to enhance the device density. In a power MOSFET, each drain region is formed on the back-side of a chip, and each source region and each gate are formed on the front-side of the chip. The drain regions of the transistors are connected in parallel so as to endure a considerable large current.
A working loss of the trench MOSFET may be divided into a switching loss and a conducting loss, wherein the switching loss caused by the input capacitance Ciss is going up as the operation frequency is increased. The input capacitance Ciss includes a gate-to-source capacitance Cgs and a gate-to-drain capacitance Cgd.
A conventional practice is to form a gate electrode and a shielded gate electrode inside a trench. The shielded gate electrode is located below the gate electrode, an insulating layer is separated the gate electrode from the shielded gate electrode, and the shielded gate electrode is connected to the source electrode. Although such practice may reduce the gate-to-drain capacitance Cgd, it increases the gate-to-source capacitance Cgs on the other hand, and is unable to effectively lower the switching loss.